mmmatthew
Rookie Solder Flinger
Posts: 12
Likes: 0
|
Post by mmmatthew on Mar 2, 2007 12:32:01 GMT -5
Hi, everyone... I'm new to these boards, so go easy on me! ;D
Anyway, I'm using an Am Dlx Strat with S-1 switching. I just noticed that when you turn down the volume knob the slightest bit, it starts making a really loud hiss (compared to when the volume was @ max). This hiss is, of course, a lot more evident when the tone is turned down.
Is this at all abnormal?
|
|
|
|
Post by Mini-Strat_Maine on Mar 2, 2007 18:18:50 GMT -5
Hi, mmmatthew, and welcome to GN2. Is that hiss evident only while the pot is being turned, and does it occur when it's turned in either direction? (You mentioned turning it down, so I'm just making sure.) And could it be a "crackle" rather than a "hiss" noise? (Not to get too caught up in descriptions or anything.*  ) My first guess would be some dirt in the pot, so that's what these questions are aimed towards. If it's "scratchy" or crackling, that's one possibility, anyway. -- Doug *Are those knights saying "nee," "neep," or "neet"? ;D |
|
mmmatthew
Rookie Solder Flinger
Posts: 12
Likes: 0
|
Post by mmmatthew on Mar 3, 2007 14:23:35 GMT -5
Hey... thanks for the reply and welcome.
The hiss only starts when the volume pot is turned to almost anything less than max, and it's continuous (not a crackle or anything and continues regardless of whether I'm touching it or not).
|
|
|
|
Post by Mini-Strat_Maine on Mar 3, 2007 15:05:24 GMT -5
Hey... thanks for the reply and welcome. Yeah, The Boss Lady hid the fireworks on me after I burned my thumb while messing around with a bottle rocket on New Year's Eve. She didn't hide them all that well, though.  Hmm, weird. (Which is another way of saying "I dunno what could cause that."  ) My next-best guess would be something about the lower resistance of the volume pot at "10" somehow doing something that kills off the frequency of that hiss. I know that doesn't even qualify as a SWAG (Scientific Wild-A'd Guess), but it should get a conversation going about this. Well, you were just itching to open it up and see what it's got for shielding, right? I'm sure one or more of the other guys will pop in now and offer some better suggestions. |
|
prohall
Rookie Solder Flinger
Posts: 1
Likes: 0
|
Post by prohall on Oct 3, 2007 10:01:24 GMT -5
Greetings all....
Was this issue resolved? If so, what was the resolution?
I'm having the exact same problem following shielding and moving tone control to the bridge.
Thanks,
Pete
|
|
|
|
Post by sumgai on Oct 3, 2007 12:11:50 GMT -5
Pete, Hi, and welcome to the NutzHouse! ;D (Sorry, no fireworks for you - our resident blow-em-up meister has gone AWOL.  ) No, somehow this particular topic dropped through a hole as big as Lars's ego. I'll have to take responsibility for that one, it happened on my watch. Sigh. So....... matt and Pete, what we need here is a sound sample of this hissing noise. Are either of you able to record and post such a thing? I have the same axe, as do ChrisK and a few others here, and I've never heard of such a thing, not from this model, nor from any other guitar. The one thing that will be unique to each of you, and different from all other players, is your playing environment and equipment. IOW, do you get the same results no matter what cord you use, no matter what amp, no matter where you are playing? If there are pedals in the circuit, do you still get the noise without them? Answers and samples are needed before further triage, so the balls are in your (repective) courts. HTH sumgai |
|
|
|
Post by JohnH on Oct 3, 2007 23:01:03 GMT -5
I’ve also come across this effect, when feeding into an amp at high gain. It’s a hiss rather than a hum, as noted above. It seems to be hiss generated within or around the amp input stage, and amplified afterwards. With a grounded input or low impedance input, the input stage seems to be better able to control this hiss, while as the guitar volume pot is reduced, the amp input is seeing a higher impedance and so the hiss is higher. As you can tell, I don’t know why it happens.
John
|
|
|
|
Post by sumgai on Oct 4, 2007 3:36:10 GMT -5
John, Ah, but you have hit the nail squarely on the head! ;D Indeed, I would suspect it is not the guitar, but instead it would be the amp. This could be exacerbated by one or more hi-gain stages between the guitar and the amp's input, regardless of the effect's actual purpose. Under normal circumstances, the grid/base/gate of the first amplifier stage is pretty close to ground (in AC analysis), but that depends on the setting of the volume pot. If the pot increases the resistance to ground, and if there is signficant capacitance in parallel with it (such as found within the connecting cord), then there's nothing to dampen the amplfying device's internally generated noise. Such noise usually manifests itself as a rushing or possibly a hiss. It will be amplified and passed on down the line, as you well know by now. There are various cures, depending on the circumstances, but the most obvious one is to reduce the input gain. If that has no effect, then it's time to insert either a small capacitor in parallel with the grid bias resistor, or to increase that resistor's value. Neither solution is particularly desirable, they change the device's operating parameters, almost always for the worse. It's also possible that the input amplifier stage is actually going bad. If it's a tube, that's easy to test. If it's a transistor or an IC, the troubleshooting is a bit more difficult.  HTH sumgai |
|
|
|
Post by JohnH on Oct 4, 2007 21:55:57 GMT -5
Sumgai, thanks, that is interesting. I noticed this effect in testing my hi-gain stompbox schemes. It occured most when i put an input 'gain' pot right at the input, and was much better when there was low-gain buffer stage at the input, with the 'gain' pot after that. I wonder if a buffer circuit could be a general answer, to keep impedance as seen by the amp input low, at all volume levels?
John
|
|
|
|
Post by sumgai on Oct 5, 2007 4:14:22 GMT -5
John, Part of the buffer being able to keep the impedance constant is the fact that it swamps the cable's capacitance, relegating that factor to a negligible value. The overall effect is that the amp's first stage always sees the same value impedance, hopefully at or near the designer's ideal value. In turn, the input stage's frequency response, both to signal and to noise, is much more uniform across the spectrum - a very desirable trick to pull off.  Bottom line: buffer good, raw bad. <insert image of James Hetfield here> ;D HTH sumgai |
|
)
)
)
